A sheet of carbon atoms folds by applying water along the red lines, then can be used to store hydrogen atoms, say mechanical engineers at the University of Maryland.

Abstract:
Just when you thought your origami skills couldn't be beat - try using the world's thinnest material, making the origami fold and unfold itself, and packing more inside than anyone expected. Researchers from the University of Maryland have done just that.

A sheet of carbon atoms folds itself into a box that opens and closes as an electric field is applied. This graphene "nanocage" could hold high densities of hydrogen for energy storage, say its inventors in the department of mechanical engineering at the University of Maryland.

Graphene is the world's thinnest material, just one atom thick. Mechanical engineers Shuze Zhu and Teng Li have found that they can make tiny squares of graphene fold into a box, which will open and close itself in response to an electric charge.

Inside the box, they've tucked hydrogen atoms, and have done so more efficiently than was thought possible. The U.S. Department of Energy is searching for ways to make storing energy with hydrogen a practical possibility, and they set up some goals: by 2017, the Department had hoped that a research team could pack in 5.5 percent hydrogen by weight, and that by 2020, it could be stretched to 7.5 percent.

Li's team has already crossed that threshold, with a hydrogen storage density of 9.5 percent hydrogen by weight. The team has also demonstrated the potential to reach an even higher density, a future research goal.

"Just like paper origami that can make complicated 3-D structures from 2-D paper, graphene origami allows us to design and fabricate carbon nanostructures that are not naturally existing but of desirable properties," said Li. "We have made nano-baskets, as well as these new nano-cages to hold hydrogen and other molecular cargos."

The U.S. National Science Foundation supported the team's research, which will be published in the journal ACS Nano.

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About University of MarylandThe University of Maryland is the state's flagship university and one of the nation's preeminent public research universities. A global leader in research, entrepreneurship and innovation, the university is home to more than 37,000 students, 9,000 faculty and staff, and 250 academic programs. Its faculty includes three Nobel laureates, two Pulitzer Prize winners, 49 members of the national academies and scores of Fulbright scholars. The institution has a $1.8 billion operating budget, secures $500 million annually in external research funding and recently completed a $1 billion dollar fundraising campaign.